One type of fracturing method involves setting a series of plugs that have progressively larger ball seats. As the lowest zone is fracked a ball is dropped to effectively isolate the interval just fracked and pressure is applied to the seated ball so that that the next interval above in the borehole can be fracked. This process is repeated with progressively larger balls that sequentially land on seats on plugs moving closer to the surface. Eventually all the intervals are fractured and the various plugs need to be removed for producing the interval. More prevalent currently is a fracturing method where a plug is set, the borehole is perforated, a ball is circulated ball onto the plug, pressure is built up to treat the zone; then another plug is set above the recently treated zone and the process is repeated. In this method the seats and matching balls do not need to be progressively larger because there are no balls to pass through other plugs. Instead each ball lands on its own plug directly without having to pass through restrictions in other plugs.
Controlled electrolytic materials have been described in US Publication 2011/0136707 and related applications filed the same day. The related applications are incorporated by reference herein as though fully set forth. The listed published application specification and drawings are literally included in this specification to provide an understanding of the materials considered to be encompassed by the term “controlled electrolytic materials” or CEM for short. These materials have been used to make barriers disintegrate in fracking applications.
The frack plugs in the past have had anchoring slips that feature wickers and hardened inserts to obtain sufficient grip to withstand the high differential pressures that are seen in fracking operations. These slips were necessarily of a material that would not disintegrate. This caused imperfect removal of the plugs after fracturing and before production. The present invention addresses this issue by using a plug design that features radial expansion and anchoring rings and a seal that are set in that manner, where the anchoring rings rely on friction forces to resist differential pressures during fracking but thereafter can disintegrate so that subsequent production is not inhibited by incomplete removal of the fracking barriers. While fracking is the preferred use other well treating applications are contemplated. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the description of the preferred embodiments and associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.